1. Field of the Invention
The present invention relates to an ultrasonic transducer that includes a single transducer and can be used to transmit/receive broadband ultrasonic waves.
2. Related Art Statement
In the field of medical care, ultrasonic diagnostic equipment having the following function has been developed: ultrasonic pulses transmitted by an ultrasonic transducer are repeatedly applied to tissues, the echoes of the ultrasonic pulses reflected by the tissues are received with the ultrasonic transducer or another ultrasonic transducer, the direction that the ultrasonic pulses are transmitted or received is gradually varied, and information obtained in a plurality of directions of the tissues is converted into visible images to display ultrasonic images.
Among ultrasonic transducers used for ultrasonic probes for the ultrasonic diagnostic equipment, an ultrasonic transducer having the structure shown in FIG. 9 is conventionally known. Electrodes 42 are each disposed on both faces of an piezoelectric transducer 41 that has been polished so as to have a uniform thickness and has uniform composition, a matching layer 43 and an acoustic lens 44 are disposed on an ultrasonic wave transmitting/receiving face which is one of the above faces of the piezoelectric transducer 41 in that order, a backing layer 45 is disposed on the other face, and these components are housed in a housing 46. The electrodes 42 disposed on both faces of the piezoelectric transducer 41 are electrically connected to an observation unit via wiring lines and connectors which are not shown.
In general, in the observation of ultrasonic images obtained using such ultrasonic probes, high-frequency ultrasonic waves are used in many cases depending on the need that high-resolution is required even if penetration is sacrificed when shallow areas are observed, and low-frequency ultrasonic waves are used in many cases when high penetration is necessary. There is a request to observe ultrasonic images using a single probe while the ultrasonic wave frequency is varied. Therefore, in order to transmit/receive more broadband ultrasonic waves, the following elements have been proposed: a composite piezoelectric element 51, equipped with a resin layer 51a and minute piezoelectric sub-elements 51b arranged therein, having broadband characteristics, as shown in FIG. 10; and a so-called plano-concave transducer 61 including a piezoelectric material having a thickness gradient, as shown in FIG. 11.